Hyperglycemia, that is, elevated plasma glucose, is a hallmark of diabetes. Plasma glucose is normally filtered in the kidney in the glomerulus but is actively reabsorbed in the proximal tubule (kidney). Sodium-dependent glucose co-transporter SGLT2 appears to be the major transporter responsible for the reuptake of glucose at this site. The SGLT inhibitor phlorizin, and closely related analogs, inhibit this reuptake process in diabetic rodents and dogs, resulting in normalization of plasma glucose levels by promoting glucose excretion without hypoglycemic side effects. Long term (6 month) treatment of Zucker diabetic rats with an SGLT2 inhibitor has been reported to improve insulin response to glycemia, improve insulin sensitivity, and delay the onset of nephropathy and neuropathy in these animals, with no detectable pathology in the kidney and no electrolyte imbalance in plasma. Selective inhibition of SGLT2 in diabetic patients would be expected to normalize plasma glucose by enhancing the excretion of glucose in the urine, thereby improving insulin sensitivity and delaying the development of diabetic complications.
The treatment of diabetes is an important health concern and despite a wide range of available therapies, the epidemic continues. Type 2 diabetes (T2DM) is a progressive disease caused by insulin resistance and decreased pancreatic β-cell function. Insulin is produced by the pancreatic β-cell and mediates cellular glucose uptake and clearance. Insulin resistance is characterized by the lack of response to the actions of this hormone which results in decreased cellular clearance of glucose from the circulation and overproduction of glucose by the liver.
The currently available therapies to treat type 2 diabetes augment the action or delivery of insulin to lower blood glucose. However, despite therapy, many patients do not achieve control of their type 2 diabetes. According to the National Health and Nutrition Examination Survey (NHANES) III, only 36% of type 2 diabetics achieve glycemic control defined as a A1C<7.0% with current therapies. In an effort to treat type 2 diabetes, aggressive therapy with multiple pharmacologic agents may be prescribed. The use of insulin plus oral agents has increased from approximately 3 to 11% from NHANES II to III.
Thus, treatment of hyperglycemia in type 2 diabetes (T2DM) remains a major challenge, particularly in patients who require insulin as the disease progresses. Various combinations of insulin with oral anti-diabetic agents (OADs) have been investigated in recent years, and an increasing number of patients have been placed on these regimens. Poulsen, M. K. et al., “The combined effect of triple therapy with rosiglitazone, metformin, and insulin in type 2 diabetic patients”, Diabetes Care, 26 (12):3273-3279 (2003); Buse, J., “Combining insulin and oral agents”, Am. J. Med., 108 (Supp. 6a):23S-32S (2000). Often, these combination therapies become less effective in controlling hyperglycemia over time, particularly as weight gain and worsening insulin resistance impair insulin response pathways.
Hypoglycemia, weight gain, and subsequent increased insulin resistance are significant factors that limit optimal titration and effectiveness of insulin. (Holman, R. R. et al., “Addition of biphasic, prandial, or basal insulin to oral therapy in type 2 diabetes”, N. Engl. J. Med., 357 (17):1716-1730 (2007)). Weight gain with insulin therapy is predominantly a consequence of the reduction of glucosuria, and is thought to be proportional to the correction of glycemia. (Makimattila, S. et al., “Causes of weight gain during insulin therapy with and without metformin in patients with Type II diabetes mellitus”, Diabetologia, 42 (4):406-412 (1999)). Insulin drives weight gain when used alone or with OADs. (Buse, J., supra). In some cases, intensive insulin therapy may worsen lipid overload and complicate progression of the disease through a spiral of caloric surplus, hyperinsulinemia, increased lipogenesis, increased adipocity, increased insulin resistance, beta-cell toxicity, and hyperglycemia. (Unger, R. H., “Reinventing type 2 diabetes: pathogenesis, treatment, and prevention”, JAMA, 299 (10):1185-1187 (2008)). Among commonly used OADs, thiazolidinediones (TZDs) and sulfonylureas intrinsically contribute to weight gain as glucosuria dissipates with improved glycemic control. Weight gain is less prominent with metformin, acting through suppression of hepatic glucose output, or with incretin-based DPP-4 inhibitors. Overall, there is a pressing need for novel agents that can be safely added to insulin-dependent therapies to help achieve glycemic targets without increasing the risks of weight gain or hypoglycemia.
A novel approach to treating hyperglycemia involves targeting transporters for glucose reabsorption in the kidney. (Kanai, Y. et al., “The human kidney low affinity Na+/glucose cotransporter SGLT2. Delineation of the major renal reabsorptive mechanism for D-glucose”, J. Clin. Invest., 93 (1):397-404 (1994)). Agents that selectively block the sodium-glucose cotransporter 2 (SGLT2) located in the proximal tubule of the kidney can inhibit reabsorption of glucose and induce its elimination through urinary excretion. (Brown, G. K., “Glucose transporters: structure, function and consequences of deficiency”, J. Inherit. Metab. Dis., 23 (3):237-246 (2000)). SGLT2 inhibition has been shown in pre-clinical models to lower blood glucose independently of insulin. (Han, S. et al., “Dapagliflozin, a selective SGLT2 inhibitor, improves glucose homeostasis in normal and diabetic rats”, Diabetes, 57 (6):1723-1729 (2008); Katsuno, K. et al., “Sergliflozin, a novel selective inhibitor of low-affinity sodium glucose cotransporter (SGLT2), validates the critical role of SGLT2 in renal glucose reabsorption and modulates plasma glucose level”, J. Pharmacol. Exp. Ther., 320 (1):323-330 (2007)).
Dapagliflozin (which is disclosed in U.S. Pat. No. 6,515,117) is an inhibitor of sodium-glucose reabsorption by the kidney, by inhibiting SGLT2, which results in an increased excretion of glucose in the urine. This effect lowers plasma glucose in an insulin-independent manner.
Dapagliflozin is currently undergoing clinical development for treatment of type 2 diabetes. (Han, S. et al., supra; Meng, W. et al., “Discovery of dapagliflozin: a potent, selective renal sodium-dependent glucose cotransporter 2 (SGLT2) inhibitor for the treatment of type 2 diabetes”, J. Med. Chem., 51 (5):1145-1149 (2008)). Phase 2a and 2b studies with dapagliflozin have demonstrated efficacy in reducing hyperglycemia either alone or in combination with metformin in patients with T2DM. (Komoroski, B. et al., “Dapagliflozin, a novel, selective SGLT2 inhibitor, improved glycemic control over 2 weeks in patients with type 2 diabetes mellitus”, Clin. Pharmacol. Ther., 85 (5):513-519 (2009); List, J. F. et al., “Dapagliflozin-induced glucosuria is accompanied by weight loss in type 2 diabetic patients”, 68th Scientific Sessions of the American Diabetes Association, San Francisco, Calif., Jun. 6-10, 2008, Presentation No. 0461P).
It has been found that dapagliflozin does not act through insulin signaling pathways and is effective in controlling blood sugar in patients whose insulin signaling pathways do not work well. This applies to extremes of insulin resistance, in type 2 diabetes as well as in insulin resistance syndromes, caused by, for example, mutations in the insulin receptor.